Chronic pain is a significant problem for people receiving opioid agonist therapy (OAT) for opioid dependence - i.e., buprenorphine/ naloxone (BUP) and methadone maintenance treatment (MMT). At least half of patients receiving BUP and MMT have chronic pain. Chronic pain is associated with pain-related disability, psychiatric problems, physical problems, and increased likelihood of misuse of opioids or other illicit drugs in this population, often leading providers to terminate treatment. Pharmacologic pain treatment in OAT patients is complicated by issues such as opioid-induced hyperalgesia, increased tolerance of opioids, other substance use, and patients' own fears about medications and addiction. Hatha yoga may be a beneficial adjunctive approach to treating chronic pain, decreasing pain-related disability, and preventing opioid misuse during OAT. Yoga includes benefits of relaxation training, physical activity, and mindfulness training in a unified practice. Yoga is a promising approach for treating chronic pain in people enrolled in OAT because: 1) yoga has evidence supporting its ability to reduce pain-related disability and pain severity in other populations; 2) there are plausible cognitive/affective and behavioral mechanisms by which yoga may reduce chronic pain, decrease pain-related disability, and reduce opioid misuse; 3) yoga is increasingly available; and 4) yoga can complement other types of pain and substance use treatment. We propose to conduct treatment development research that would prepare us to study whether yoga (vs. a health education control group) might be an effective adjunctive treatment for pain in people enrolled in OAT for opioid use disorders. We hypothesize that, relative to a control group, yoga will: decrease pain-related disability (primary outcome), decrease pain, and decrease opioid misuse. This project will include two phases. In phase 1 (Treatment Development Stage 1A), we will use feedback from patient focus groups (n= 24 patients) and experts to refine our current hatha yoga intervention and health education intervention for specific use in people enrolled in OAT with chronic pain. In phase 2 (Treatment Development Stage 1B), we will conduct a pilot randomized clinical trial (n = 60) of yoga vs. health education groups (attention control) for persons with chronic pain who enrolled in OAT. Participants will be enrolled in the active intervention for 3 months, and then be followed for 6 months. Specifically, we will assess feasibility, acceptability, and safety of both the active intervention and control groups; assess differences between groups on outcomes (within relevant confidence intervals); examine changes on potential mechanisms of action, including mindfulness, pain catastrophizing, depression, and anxiety; and examine whether amount (dosage) of yoga practice is related to key outcomes. This project will provide us with materials, experience, and pilot data necessary for the next stage of this line of research, namely, a fully powered randomized clinical trial. Hatha yoga has a potential to decrease pain-related disability, pain severity, and opioid misuse in this population of people with difficult-to treat chronic pain.